1. Field of the Invention
The present invention relates to a scanning probe microscope in which characteristic information of a scanner is automatically set concurrently with replacement of the scanner.
2. Description of the Related Art
A scanning probe (SPM) is an apparatus for observing a physical quantity of a sample surface with extremely high resolution at sub-nanometer scale by scanning the sample surface with a probe having an acuminated tip end and detecting mechanical, electrical, magnetic interaction, or the like acting between a probe and the sample surface.
For example, in an atomic force microscope (AFM) as a representative SPM, using a probe unit having a micro-cantilever and a probe mounted on one end thereof, a force such as an atomic force acting between the probe tip end and the sample surface is detected from the change in deflection amount of the cantilever. For the detection of the change in deflection amount, for example, a system by which a voltage is applied to a piezoelectric scanner that expands and contracts in the height direction (hereinafter, referred to as “z direction”) so that the deflection amount becomes constant and this applied voltage is used as a detection value, and the like is adopted. Since this voltage value cancels the height direction displacement, the voltage value corresponds to the sample surface height information in the position where the probe is opposed.
This AFM apparatus includes a scanner having a piezoelectric element, a probe unit, and a probe displacement detection unit. As a specific arrangement example, a sample is mounted on the stage to be driven and displaced by the scanner, the probe unit is set immediately above the sample surface, and the photoelectric probe displacement detection unit applying the principle of an optical lever is disposed above the probe unit, i.e., on the back face of the cantilever. Observation is performed while displacing the probe tip end and the sample relatively by allowing the scanner to perform the raster two-dimensional scanning, which is a combination of main scanning and sub-scanning, in the horizontal direction (hereinafter, referred to as XY direction). The displacement detection values are paired with the associated scanning positions of the scanner to display an image on the display and, therefore, a scanning microscope image having subnano scale resolution can be obtained.
FIG. 6 is a diagram showing a basic schematic of the conventional SPM. To a base 101, a cylindrical piezoelectric element 102 as a scanner drive unit is fixed with its central axis is made perpendicular to the base surface. A stage 103 is provided on the free end side of the cylindrical piezoelectric element 102, and a sample 104 is mounted on the stage 103. A probe unit 105 is a cantilever having an acuminated probe on the free end thereof manufactured by a silicon process, for example, in an atomic force microscope, and is disposed above the sample 104. The base 101 is fixed on a z coarse stage 106 for bringing the sample 104 surface and the probe tip end of the probe unit 105 close to each other. Above the probe unit 105, a probe displacement detection means 107 including a laser source and a photoelectric detector capable of two-dimensionally detecting a laser spot position is disposed.
The output signal of the probe displacement detection means 107 is input to a feedback circuit 108. The output of the feedback circuit 108 is an input to the cylindrical piezoelectric element 102 as a z direction drive voltage. Further, in the cylindrical piezoelectric element 102, an XY scanning signal is received from an XY scanning circuit 109, resulting in the mounted sample 104 being two-dimensionally displaced via the stage 103. The XY scanning signal from the XY scanning circuit 109 is simultaneously received by a display unit 110, and the z direction drive voltage corresponding to the detection signal is also received by the display unit 110, thereby allowing a typographic image of the sample 104 surface to be obtained (see Publication of Japanese Patent Application No. 2002-350319).
In the foregoing conventional SPM, the scanning is sometimes replaced according to use conditions. Since scanners have different characteristics from one to another, when replacing the scanner with another scanner, various parameters such as a piezoelectric constant and an nonlinear correction coefficient of the scanner should be se in a controller for controlling operation of the SPM (computer in general). Generally, there has been a problem that, since this setting is manually performed by an operator and its operation is not only complex, but also easily accompanied by errors, when the setting is erroneous, accurate measurements can not be performed. Problems such that the XY scanning is not performed in a designated manner, the z displacement amount is deviated, and the scale of the obtained microscopic image is varied have occurred.